The present invention relates to a controller for an internal combustion engine.
Japanese Laid-Open Patent Publication No. 2015-121231 discloses a controller that controls the energizing of a fuel injection valve, which injects fuel into a combustion chamber of an internal combustion engine. The fuel injection valve includes a valve member that opens when the fuel injection valve is energized to inject fuel. The fuel injection valve performs partial lift injection or full lift injection. When the partial lift injection is performed, the fuel injection valve is energized to move the valve member in a valve opening direction and de-energized before the valve member reaches a fully open position. When the full lift injection is performed, the fuel injection valve is energized to move the valve member in the valve opening direction and de-energized after the valve member reaches the fully open position.
The above controller calculates a request fuel injection amount, which is a request value of the amount of fuel injected from the fuel injection valve for each combustion performed in the combustion chamber, in accordance with the driving state of the internal combustion engine. The fuel injection valve injects fuel corresponding to the request fuel injection amount by performing the partial lift injection or the full lift injection. In the partial lift injection and the full lift injection, fuel pressure, which is the pressure of the fuel supplied to the fuel injection valve, changes the relationship of the energizing time of the fuel injection valve and the fuel injection amount. Thus, when performing the partial lift injection and the full lift injection, the internal combustion engine controller calculates the energizing time of the fuel injection valve based on the fuel pressure and the request fuel injection amount.
As described above, the fuel pressure needs to be reflected on the calculation of the energizing time. In the partial lift injection, the fuel injection valve is de-energized before the valve member reaches the fully open position. Thus, a valve opening delay of the valve member when the fuel injection valve is energized and the valve opening speed of the valve member will greatly affect the injection amount. Additionally, the fuel pressure when the energizing is started greatly affects the valve opening delay and the valve opening speed. When the full lift injection is performed, the energizing time is long, and a large amount of fuel is injected with the valve member located at the fully open position. Thus, a valve opening delay or a valve opening speed of the valve member subtly affects the injection amount. However, since a large amount of fuel is injected, fuel is continuously injected. This increases the reduction rate of the fuel pressure. Thus, changes in the fuel pressure that occur during the fuel injection need to be considered when the energizing time is calculated in the full lift injection.
As described above, the fuel pressure affects the relationship of the energizing time and the fuel injection amount in manners that differ between the partial lift injection and the full lift injection. Thus, to improve the accuracy for controlling the amount of fuel injected from the fuel injection valve, it is desired that the differences in the effect of the fuel pressure be considered when calculating the energizing time for each of the partial lift injection and the full lift injection. However, Japanese Laid-Open Patent Publication No. 2015-121231 includes no teaching of such calculations.